The present invention relates to apparatus for extracting samples of a fluidic product from process lines, pipes or vessels.
Certain manufacturing operations require that the immediate or overall composition of a liquid or fluid product flowing through a process line or contained within a vessel or tank be monitored. Such monitoring ordinarily is accomplished with sampling apparatus, which takes samples of product from a main body of the product Where a composite sample is required, the sampler may be periodically operated to withdraw a series of measured samples of product passing a sampling point. The series of samples are collected and admixed to form a representative sample of the total volume of product
Other uses for samplers are in on-line analysis applications, in which the immediate composition of a product must be determined. For this application, the individual samples are not collected as a composite sample, but instead are analyzed separately.
Four exemplary types of prior sampling apparatus are disclosed in U.S. Pat. Nos. 4,147,062, 4,262,533, 4,475,410 and 4,744,255, issued to Ben E. Jaeger, the present inventor and teachings of which are incorporated herein by reference. Sampling apparatus of the type disclosed in said patents is attached to a port to a process line or vessel containing the liquid or fluid product. This enables a product sample obtaining recess in a plunger of the sampler to be extended into the product to receive a product sample in the recess. The plunger is then retracted to deliver the product sample to a collection point in the sampler.
The access line usually is attached to the product-containing process line by an adapter connected and sealed to the process line around an opening therein. The sampler may include, as described in said Jaeger patents, a sampler body having a bore in which a plunger having a sample obtaining recess is reciprocated. The bore communicates with the process line interior through the adapter and process line opening. The plunger is reciprocated to a sample obtaining position in which the plunger recess is extended out of the body bore and into the process line to receive a sample of the product therein. The plunger is then reciprocated to a sample delivering position in which the plunger recess is retracted into the bore to deliver the sample to a point in the bore where the sample is removed from the recess and collected.
The interior of the vessel or process line is a pressure boundary of the vessel, pipe or process line and the exterior is outside of the pressure boundary. The process line defines within its inner walls a flow path for the product. The product does not necessarily flow through the entire cross-sectional area of the flow path, so a flow stream of the product, which is the normal continuous flow path of the fluid product through the process line, is within and of the same or a smaller cross-sectional area than the flow path. The sampler adapter that communicates with the opening to the process line may comprise a recessed tee or pullout, the recessed portion of which is part of and within the interior of the process line and therefore within the pressure boundary.
The fluid product flows through the process line in the flow stream. The product may be a liquid or a fluidized solid that is highly viscous, stringy, gummy or abrasive, and its solids content may be a soft granular material that is generally gummy, a stringy fibrous material such as paper pulp, or a hard and abrasive material such as sand. Depending upon the nature of the product, it can build up on, deposit on, or stagnate adjacent to and along the inner walls of the process line. This results in a dead layer of the product on and along the process line inner walls and in the cross-sectional area of the flow stream often being smaller than the cross-sectional area of the flow path through the process line. The flow stream then exists inwardly from the inner walls of the process line and the dead layer of product. A deposited layer of the solids component of the product on the process line inner walls can be caused by density differences between the solids and the liquid components of the product, which can result in stratification of the product and settling out of solids along the product flow path through the process line. Should the product comprise a stringy fibrous material such a paper pulp, a layer of the solids component can build up on the process line inner walls as a result of dewatering of the solids component as the flow rate of the product, adjacent to the walls, slows relative to the flow rate toward the center of the flow stream. Also, a boundary layer of relatively stagnant product can occur if the product is highly viscous but otherwise homogeneous and clean. A highly viscous product exhibits a flow distribution curve that is characterized by the product having that a velocity that approaches zero at the inner walls of the process line and increases to a maximum at the center of the flow stream.
With fluid products that deposit and build up in a layer on inner walls of process lines, the thickness of the layer can increase and move inward, resulting in a progressive decrease in the cross-sectional area of the product flow stream. This, in turn, can result in a progressive decrease in the flow rate of product through the process line which, if allowed to continue, could result in significant blockage of the line. With such products, from time to time it often is necessary to pass scarifying plugs through the process lines to clean built up of material from the walls of the lines.
Samplers of the types disclosed in the aforementioned Jaeger patents may be used to sample fluid products that tend to deposit and build up or otherwise form a dead layer of product on inner walls of process lines. Because it may be necessary from time to time to pass scarifying plugs through a process line to remove built up of product, such a sampler must be coupled to the line so that its forward end does not normally protrude into the interior of the line. This is necessary to prevent the sampler forward end from blocking passage of any scarifying plugs. However, as product builds up in the process line and moves radially inward from the sampler forward end, the sampler and its plunger gradually and effectively become spaced further and further from the flow stream of product that exists toward the center of the line inwardly of the dead layer of product. This is not a desirable situation, since during a sampling operation the forward end of the sampler may be sufficiently far away from the flow stream that the sample obtaining recess in the plunger cannot be projected fully past the built up thickness of product into the flow stream. The result is that the product sample obtained may not be a valid representation of the product in the flow stream. Also, even if the plunger recess can be projected fully into the flow stream, upon retraction it will pass through the dead layer of product, which can result in contamination of the sample.
Even if the product sampled is not of the type that builds up on and must be removed from inner walls of a process line by scarifying plugs, the samplers of the aforementioned Jaeger types may not necessarily obtain product samples that are valid representations of the product in the flow stream. This can occur, for example, if the fluid product is highly viscous, such that its flow component toward the inner walls of the line is slower than toward the center of the flow stream. In this case, unless the sample delivering recess in the plunger can be projected beyond the dead layer comprising the stagnant slow or no flow rate portion of the flow stream, a valid product sample may not be obtained. Nor can this problem be properly overcome by mounting the sampler so that its forward end is always within the flow stream in the process line, since this could, and often would, undesirably decrease the cross-sectional flow area of and create turbulence in the flow stream.
An object of the present invention is to provide a fluid sampler of the reciprocating plunger type, that is adapted to be coupled to and obtain valid product samples from a process line in which there is a flow of a product that tends to build up on, deposit on or stagnate along inner walls surfaces of the process line in a dead layer of product
Another object is to provide such a sampler, a body portion of which has a forward end that can selectively be positioned either to the exterior or to the interior of a flow stream of product through the process line.
Yet another object is to provide such a sampler, the forward end of the body of which can be positioned at selected locations within the interior of the process line.
A further object of the invention is to provide such a sampler in which the forward end of the sampler body may be positioned within the process line inward from a dead layer of product on inner walls of the process line during a sampling operation, to obtain a valid product sample from a flow stream of the product toward an axial center of the process line and without contamination of the sample by product from the dead layer.
In accordance with the present invention, a fluid sampling apparatus is operable to obtain discrete samples of fluid product from a process line. The sampling apparatus includes a sampler body having a bore with a forward opening at a forward end of the sampler body. A plunger in the sampler body bore has a fluid product sample-receiver, and an adapter connects the sampling apparatus to the process line at an opening to the process line. A motor reciprocates the sampler body between a first position where the forward end of the sampler body is retracted to the exterior of a product flow stream through the process line and a second position where the forward end is extended into the interior of the flow stream. The motor also reciprocates the plunger in the bore between a sample obtaining position where the plunger sample receiver is extended out of the forward bore opening into the flow stream to obtain in the sample receiver a sample of product, and a sample delivering position where the sample receiver is retracted from the flow stream to a position within the bore where the product sample is collected.
The motor reciprocates the plunger between the sample obtaining and sample delivering positions when the sampler body has been reciprocated to the second position where the forward end of the body extends into the product flow stream. The sample receiver may be an annular recess in and circumferentially around the plunger, and seals on the plunger maintain a fluid seal between the sampler body bore forward opening and the sample delivering position during reciprocation of the plunger.
In the disclosed embodiment, the motor includes first and second motors. The first motor reciprocates the sampler body to move the sampler body forward end between its first position to the exterior and its second position to the interior of the flow stream. The second motor reciprocates the plunger to move the plunger aperture between the sample obtaining and sample delivering positions. The first and second motors may comprise pneumatic motors, the second motor is coupled to the sampler body and to the plunger and the first motor is coupled to the second motor. The second motor reciprocates the plunger relative to the sampler body and process line, and the first motor reciprocates the second motor, the plunger and the sampler body relative to the process line. The second motor has a piston in a cylinder, the cylinder is attached to the sampler body and the piston is attached to a rearward end of the plunger to reciprocate the plunger relative to the sampler body and between the sample obtaining and delivering positions. The first motor has a cylinder, a piston in the cylinder and a piston rod attached at its rearward end to a forward end of the piston and at its forward end to the cylinder of the second motor to reciprocate the second motor, the plunger assembly and the sampler body. The first motor is rearward of the second motor and the piston rod of the first motor and the plunger are axially aligned.
The sampling apparatus is adapted to obtain samples of a fluid product of a type that tends to build up, deposit or stagnate on and along inner walls of the process line in a dead layer of product The adapter connects the sampler body to the process line in sealed relation to the process line opening for reciprocation of the sampler body, by the first motor, forward from the first position to the second position within the product flow stream inwardly of the dead layer of product, and then rearward from the second to the first position to the exterior of the flow stream. With the sampler body in the second position, reciprocation of the plunger by the second motor to the sample obtaining position places the plunger recess inwardly of the dead layer of product and into the product flow stream in the process line for collection of a product sample. With the sampler body in the first position, it is out of the flow stream and main flow path through the process line and does not interfere with movement through the process line of the product flow or of any scarifying plugs that from time to time may be passed through the process line to clean any built up layer of product from the process line inner walls.
The invention also contemplates a method of sampling a fluid product conveyed through a process line. The method comprises the steps providing a sampler body having a bore and a forward opening from the bore at a forward end of the sampler body; positioning a plunger, having a sample receiver intermediate forward and rearward ends thereof, within the bore, and moving the sampler body to move its forward end between a first position to the exterior of a product flow stream through the process line and a second position within the interior of the flow stream. Also included is the step, while the sampler body forward end is at the second position, of reciprocating the plunger to extend the plunger forward through the sampler body bore to a sample obtaining position where the forward end of the plunger and the sample receiver are projected out of the forward bore opening and into the fluid product within the process line to receive in the sample receiver a sample of the product, and to then retract the plunger rearward through the sampler body bore opening and into the bore to deliver the plunger sample receiver and product sample therein to a sample delivering position in the bore. Further included are the steps of removing the sample from the recess at the sample delivering position and periodically repeating the plunger reciprocating and sampler body moving steps.
The method is advantageous for use in obtaining samples of a fluid product of a type that builds up, deposits or stagnates on and along, inner walls of the process line in a dead layer of product, and the step of moving the sampler body forward end to the second position extends the forward end into the process line inwardly beyond the dead layer of product and into the flow stream. This enables collection of a product sample that is generally free of contamination by product from the built up, deposited or stagnated dead layer. Then, when the sampler body is retracted to the first position, it is moved out of the flow stream so as not to interfere with the flow of product or movement of any scarifying plugs that may be passed through the process line.
The foregoing and other objects, advantages and features of the invention will become apparent upon a consideration of the following detailed description, when taken in conjunction with the accompanying drawings.